Hydraulic control apparatus



March 6, 1956 L. F. JAsEPH HYDRAULIC CONTROL APPARATUS Filed May 5l, 1950 2,737,197 Patented Mar, 6, 195,6

HYDRAULIC CONTROL APPARATUS Lawrence F. Jaseph, Memphis, Tenn., assignor to Dover Corporation, a corporationof Delaware Application May 31, 1950, Serial No. 165,18)

21 Claims. (Cl. 137-108) The present invention relates to improvements in a hydraulic control apparatus and more particularly to improvements in control valves for hydraulically actuated devices. The present invention is an improvement in devices of the type disclosed and claimed in my copending application Serial No. 463,191, tiled October 24, 1942, now Patent No. 2,553,045 dated May 15, 1951.

The present invention relates primarily to control valves for hydraulically actuated devices, of which an elevator may be considered to be an example. The valves are also particularly advantageous in connection with devices which are raisediby pressure obtained directly from some suitable pressure source such as a motor driven constant displacement pump and lowered by gravity.

The control device or valve of the present invention may be considered as a link between a motor driven constant displacement pump and the hydraulic motor of an elevator. itserves the following purposes: (l) to prevent return flow of liquid when the elevator travels upward and the pump is stopped as a result of power failure, belt breakage or in making normal stops at landings; (2) to govern return flow from the elevator-jack to a reservoir when the-elevator is lowered; (3) to enable the motor and pump to reach full speed before load is imposed thereonthis is achieved by bypassing the entire output of the pump when it is started and thereafter gradually diminishing and finally terminating the bypassing of the liquid; (4) to enable the elevator to be raised at a normal or high speed and then thereafter raised at a lower speed preliminary to a stopthe low speed operation being accomplished by bypassing a predetermined portion of the pump discharge so that only another predetermined portion will be supplied to the elevator jack; (5) to stop the elevator by gradually bypassing an increased vportion and finally all of the pump output so that the elevator will come to rest regardless of whether or not the pump continues in operation; and (6) to control the downward movement of the elevator for the purpose of obtaining high and low lowering speeds of the elevator.

The foregoing purposes and others are achieved by a relatively simple control .device adapted to be controlled either manually or automatically or otherwise, as desired.

One of the objects of the present invention is the provision of a new and improved hydraulic control device supplied withiluid from a motor-driven pump, which is arranged to enable the motor to lbe started and accelerated to full speed with substantially noload.

Another object of the presentinvention is to provide a new and improved over-pressure relief device.

A further object of the present invention is to provide a new and improved combined over-pressure and load controlling device.

A furtherV object of the present invention islthe provision of a new and improved control device for effecting the flow of a definite volume of liquid past an orifice or valve in an open or partially open position. n

A further object of the present invention is the provision of a new andimp'rov'ed vcontroll device of the character set forth in the preceding paragraph comprising a pair of valves controlling the ow of fluid from a pressure source to an actuated device and to a low pressure region, and more specifically, wherein one of said valves defines, in effect, an orice and is located-between the pressure source and the actuated device and the other is a bypass valve located between the pressure source and the low pressure region.

Another and more specific object of the present invention is the provision of a new and improved controldevice of the character set forth in the preceding paragraph wherein the bypass valve is controlled by a valve located between the pressure source and actuated device or downstream side of the first Valve (the orice) and is arranged to open only when the pressure differential across the said irst valve exceeds a predetermined amount.

Another object of the present invention is to provide a new and improved simplified control device for maintaining a predetermined rate of liuid flow from 'a source of iuid under pressure to a device actuated by the iiuid.

Another object of the present invention is to provide a new and improved hydraulic control device comprising a single valve utilizedfboth as a check valve for preventing flow of iluid in one direction and for controlling the flow of uid in the same direction, and more specically, wherein said valve can be operated to different positions to provide dierent rates of flow of said fluid in said one direction.

Avfurther object of the present invention is to provide a new and improved hydraulic control means comprising a throttling valve and means for moving said throttling valves to predetermined positions to control the rate of flow of fluid.

A still further object of the present invention is the provision of a new andimproved hydraulic control device as set forth in the preceding paragraph, wherein adjustment means are provided for regulating the predetermined positionsto which the valve is moved.

Other objects and advantages of the present invention will become apparent from the ensuing description of apparatus embodying the invention, in the course of which reference is had to the accompanying drawing, in which:

The figure is a diagrammatic view of an installation embodying the present invention and including across sectional view of control device.`

Before proceeding with a detailed description of the control device of the present invention, it may be well briefly to describe an installation thereof which is but one of many with which the control device may be used. It comprises a hydraulically actuated device such as an elevator, indicated as a whole by reference character it). The elevator comprises a car or platform 12 and a jack 14 to which fluid is supplied under pressure through a conduit 16. Fluid flows through the conduit from the jack back of the reservoir when the elevator is being lowered as by gravity.

Fluid Vunder pressure may be supplied from any suitable source. In the instant case, the iluid is supplied by a pump 2t? of the constant displacement type having its inlet connected through conduit 22 to a fluid reservoir 24 and its outletconnected by conduit 216 to the control device. The latter is also connected by a bypass or return conduit 2S to the reservoir. The pump Ztl may be driven in suitable manner as by a substantially constant speed electric motor 39 adapted to be placed into operation as by the closure of a suitably operated switch whenever it is desired to raise the elevator. The control for thefmotor and likewise the controls for the various controlled parts'of the control device have not been disclosed as they may take various Aforms depending upon the particular installation, as will be made apparent hereinafter.

In the illustrated embodiment of the invention, the device is provided with four electrically operated means for selectively effecting both raising and lowering at high and low speeds. These solenoids are indicated by the reference characters 32, 34, 36 and 38. When it is desired to raise the elevator at high speed, the motor 3? and solenoid 32 are energized. When it is desired to raise the elevator at slow speed, the solenoid 34 is also energized. To stop the elevator, usually the motor 30 and either or both solenoids 32 and 34 are deenergized, although deenergizing solenoid 32 alone will stop the elevator even though the motor 3l) continues to run. When it is desired to lower the elevator at high speed, the solenoid 36 is energized and when it is desired to lower the elevator at low speed, the solenoid 38 is energized. As indicated above, the switching arrangements for energizing the motor and solenoids may take various forms for different installations and they have, therefore, not been indicated.

Before proceeding with a description of the operation of the control device, it may be well brieily to set forth the main components and features of its construction. These include a bypass valve 40 movably mounted in a bypass valve port 42 located in a partition 44 between the pump outlet passage 26 and the return passage 28 and a combined check and lowering valve i) movably mounted in an outlet and return port 52 connecting passages 26 and 16. The bypass valve port thus connects the high pressure side of the system to a low pressure region and controls the flow of Huid from the high pressure to the low pressure region. The combined check and lowering valve serves to prevent return flow of fluid and to permit flow at different speeds in opposite directions for high and low speed raising and lowering. To raise the elevator the motor and solenoid 32 are energized. The bypass valve 40 is normally open so that whenever the motor is started it quickly accelerates and brings the pump up to full speed before substantially any load is imposed thereon because the iiuid is bypassed through the bypass valve at a very low pressure. After the motor has started, the bypass valve 4t) is gradually closed by an increasing uid pressure which finally closes the bypass valve.

The combined check and lowering valve Sii is normally closed by the pressure of the fluid in the conduit 16 and elevator jack 14 and the pressure of the elevator. However, as the bypass valve is gradually closed, the pressure in conduit 26 is gradually built up to a point such that the valve Si) is opened and the full output of the pump is supplied to the elevator jack to raise the elevator at high speed.

To eiect slow raising of the elevator, the solenoid 34 is also energized. Its energization results in the operation of the combined check and lowering valve 5th to an intermediate point such as that illustrated and, at the same time, the bypass valve 4l? is partially opened and its position is controlled by means including a spring loaded check valve 54 in such manner that a predetermined and desired rate of iiuid tlow is maintained across the valve Si). In other words, the bypass valve is controlled to maintain a desired pressure drop and, therefore, rate of duid How across the valve 5t?.

To stop the elevator, the motor and solenoids are deenergized whereupon the bypass valve 4t) is opened to effect stopping of the elevator independently of the inertia and rotation of the motor and pump. When the pressure in the pump outlet passage 26 decreases as a result of the pump being placed out of operation and the bypass being opened, the valve Sti is closed by the pres sure in the conduit 16, thereby to hold the elevator at the position into which it was operated.

To lower the elevator at high speed, the solenoid 36 is energized. The bypass valve is open at this time and the valve Sd is opened to a predetermined extent with the result that fluid is returned from the elevator jack to the reservoir at a rate depending upon the setting of valve 50.

To lower the elevator at a slower speed, the solenoid 36 is deenergized and solenoid 38 is energized. This results in the operation of the valve 50 to another position wherein the fluid is returned at a lesser rate from the conduit 16 to the reservoir. The construction of the primary elements of the control device will now be considered in detail, consideration being given rst to l the bypass valve.

The positioning and movement of the bypass valve are effected by a piston 56 operatively connected to the valve by a `/alve stem 58 and comprising in effect inner and outer pistons 60 and 62, the latter of which is hollow and slidably receives the inner piston 6i) and is also itself slidably mounted in a piston chamber. or cylinder 64, the outer end of which is closed by a closure cap 66. The latter is removably secured as by bolts 63 (only one of which is shown) to the cylinder deiining portion 70 of the device.

The bypass valve 4i) is rigidly secured as by a pin and thread connection to the valve stem 58. The two part piston 56 is movably secured relative to the outer end of the stem for reasons which will appear shortly. The operative connection between the piston and stem includes a disc 72 threaded onto the outer end of the valve stem and locked in position thereon by a lock nut 74.

In accordance with one of the features of the present invention, the disc 72 and inner piston 60 constitute also an overpressure relief enabling the bypass valve 40 to open in the event of excess pressures. Upon the occurrence of an excess pressure, a relatively heavy spring 76 disposed between the valve 40 and piston 60 is cornpressed to permit opening of the bypass valve. The spring is constructed not to yield under the normal working pressures but to yield only when the pressures exceed some predetermined over-load value. When the spring does yield, the disc 72 is forced away from an associated annular valve seat 78 formed at the outer end of piston 69 thereby to place the piston chamber 64, which constitutes a pressure chamber in which a pressure is built up to close the bypass valve, into communication with the reservoir or return conduit 2S, whereupon the pressure in chamber 64 is reduced and the piston 56 is forced toward the right to enable the bypass valve to open. The communication between the pressure charnber 64 and conduit 28 is through cored passages 80 in the inner piston 6G, the inner central opening 82 of the outer piston 62 and opening 84 in the casing of the control device. When the pressure decreases below the over-load value, the pressure in chamber 64 is built up in a manner to be described shortly to effect reclosure of the bypass valve.

The inner piston 60 and the effective face area of the bypass valve 4@ are equal so that when the same pressures exist in conduit 26 and pressure chamber 64, the bypass valve and piston 60 are in hydraulic balance. Under these conditions, a spring 86 moves the inner and outer pistons oppositely relative to each other to force the inner end 88 of the inner piston against an internal shoulder 9G of the outer piston.

The bypass valve is normally biased toward and maintained in its open position when the pump is not operating by a spring 92, forcing the outer piston 62 toward the right'. The spring 92 abuts against the inner end of the outer piston and against an internal shoulder 94 formed in the casing adjacent the casing opening 84.

The bypass valve is gradually closed when the motor 30 and pump 20 are started by a gradual increase in pressure in the pressure chamber 64, this gradual increase in pressure forcing the two part piston 56 to the left against the bias of spring 92. Fluid under pressure is supplied to the pressure chamber 64 at a predetermined rate through a manually adjustable needle valve 94 when the solenoid 32 is energized and to move its valve piston 96 to its indicated position in which the needle valve is :ag/raakte# s placed into communication with the pressure chamber through the internal cavity 98 in which the piston 96 is movable and a fitting 100. he inlet end of theneedle valve 94 is connected to the pump outlet conduit 26 through a tube 102 and fitting 103 so that when the solenoid 32 is energized, uid from passageway 26 ows to the pressure chamber 64 at a rate determined by the setting of the needle valve. The construction of the bypass valve 40 is such that in its open position there is a pressure drop between conduits 26 and 28 with the result that the pressure in the pressure chamber 64 tends to become equal to that in conduit 26. As a result, the piston assembly 56 and bypass valve 40 gradually move to the left to close the bypass port. The piston 60, it may be remembered, is of the same effective area as the valve so that when pressure conditions are equal, these elements are hydraulically balanced with the result that the spring 86 maintains the end 83 of piston 60 against the shoulder 90 of the hollow piston 62. The closing movement continues until the hollow piston 62 abuts against internal shoulder 104. In the vclosed position of the valve, it is preferred that there be some clearance between the end 88 of piston 60 and shoulder 90 to insure good seating of the by-pass valve.

When the pressure in conduit 26 becomes great enough to overcome the pressure due to the load upon the jack 10, the combined check and lowering valve 50 is opened against the bias exerted thereon by a spring 106v disposed between the end of the valve and a closure cap 108 removably secured to the casing by bolts 110. The valve 50 is slidably mounted on a valve stem 112, the valve having a central hollow portion 114 in which is located an enlarged end 116 of the valve stem, which end is effective to move the valve 50 to the left, the position in which the valve is shown to reduce the ow of fluid to the elevator jack for slow speed raising of the elevator. However, when the solenoid 34 is deenergized, the valve 50 moves to its fully open .position because the valve stem 112 is located somewhat to the right of where it is shown.

The position of valve 50 is controlled to effect raising of the elevator at slow speed, as well as lowering of the elevator at both high and slow speeds. Consideration will rst be given to the apparatus for positioning the valve to effect low speed raising.

The position of the valve 50 is controlled by a piston 120 having an effective area greater than that of the valve and xedly secured to the end of the valve stem as by a threaded and pinned connection. The piston is movably mounted in a cylinder 122, the inner end of which has an internal shoulder 124 and the outer end of which is closed by a closure cap 126. A pressure chamber 128 is thus provided in'back of the piston. The piston is biased to the right, by a spring 130 disposed between the piston and the closure cap,` to a position determined by engagement of a washer 132 with shoulder 124, which Washer is forced against a collar 136 secured to the valve stern by a spring 138 located between the washer and the inner yface of the piston, and which spring is stronger than the spring 130 which it etlectively opposes.

Under normal conditions, i. e., when none of the'solenoids 34, 36 or 38 are energized, equal Apressures act on the two sides of the piston. .The inner side oi' the piston is open to uid 'Ln the pump outlet conduit 26, whereas the outer side is open to fluid in the pressure chamber 128 which is at the pressure of fluid in conduit 26 because of its connection thereto through a manually adjustable needle valve.140, tube 142, and tting 103.

Prior to the time that the motor 30 is energized, the piston 120 is to the right'of where it is shown andito an extent determined by the engagement of the washer 132 with shoulder 124. In this position the enlargement 116 at the end of the valve stem is just clear of the inside surface144 of the Valve 50i sof'that'l the latter vcan be fully 6 opened by the increase in pressure in the conduit 26 without moving piston 120.

To effect slow raising of the elevator, the solenoid 34 is energized to eect movement of the valve 50 to a partially closed position such as that illustrated. The closing movement of valve 50 occurs at a rate depending upon the setting of an adjustable needle valve at the outlet side of the solenoid operated valve 34 and connected to the low pressure conduit28 through the tube 152 and fitting 154. l

The partially closed position of the valve 50 is determined by an adjustable slide valve 156 movably mounted in a bore in the closure cap 126. The slide Valve is operatively connected to the outer side of piston 120 by an adjustable screw 158 extending through it. The slide valve and screw are biased toward the right so that the screw engages the piston by a spring 160 abutting against the valve and a plug 162 closing the valve bore. The side valve is Iprevented from turning by a tangent pin 164 engaging a at 166 of the valve.

The partially closed position of valve 50 is determined by the adjustment of slide valve 156 and more particularly when the latter is at a position wherein the tlow of liquid to the pressure chamber 128 through the needle valve 140 is equal to the ow from the pressure chamber through solenoid operated valve 34 and needle valve 159. In this position of the slide valve, the outlet port 168 with which the solenoid operated valve 34 communicates and which extends to the needle valve bore is partly closed to decrease the ilow from the pressure chamber 128. It may be mentioned that that the slide valve is preferably provided with a passageway 170 communicating with the pressure chamber and port 168, relative movement between which and the port determines the rate of outflow of fluid from the pressure chamber.

rl'he combined check and lowering valve 50 is thus positioned in a partially closed position to effect raising at slow speed and in accordance with another feature of the present invention, this speed is maintained uniform by control of the bypass valve 40 to bypass more or less of the pump discharge in order to maintain a constant ow of uid past the partially closed valve 50. The bypass valve 40 is'partly opened whenever the pressure in conduit 26 exceeds the pressure in conduit 16 by a predetermined amount, which amount is the pressure required to open the spring loaded check valve S4 which was referred to some time ago. It should perhaps be noted that when the valve 50 is partly closed, the pres sure in conduit 26 rises above that in conduit 16; the pressure in the latter cannot be changed because its pressure is determined by the elevator and its load, which is .unchanging as the elevator is raised.

The spring loaded check valve is arranged to open when some relatively small pressure diiierence (such as 10 pounds per square inch) exists across it from right to left, i. e., across it from its upstream to its downstream side. When it does open, liquid from the bypass valve pressure chamber 64 is discharged through it to the conduit 16. While the pressure chamber is connected to the high pressure conduit 26, the intiow to it is restricted by the needle valve 34. The result is that liquid flows out from the pressure chamber allowing the two part piston 56 to move to the right and the bypass valve 40 to open. The resuit is partial opening of the bypass Valve 40 and a reduction in the flow from conduit 26 to conduit 16. This reduction in iiow reduces the pressure drop across the valve 50 and this drop tends to become equal to the pressure required to open the one way check valve 54. This condition of equilibrium establishes a deiinite liquid iiow past the valve 50, it being that volume which will cause a tall in pressure in passing valve 50 in its partially closed position equal to the xed adjustment of opening pressure of the check valve 54. As previously indicated, the extent of opening of the valve 50 depends on the setting of the adjustment screw in the slide valve 156.

When it is desired to stop the upward movement of the elevator, the pump driving motor 30 and the solenoid valves 32 and 34 are deenergized. The inertia of the motor and pump will cause them to rotate for a short time and if their coasting to a stop were depended on to bring the elevator to rest, the stopping distance would vary considerably with the load imposed on the elevator, By making use of the slow-down arrangement described however, the inaccuracy due to load changes in stopping distances is greatly reduced.

ln accordance with the present invention, error in stopping distance is reduced further by opening the bypass valve 40 to efiect the stopping rather than depending upon the coasting of the motor and pump. The result is a quicker stop and less variation in stopping as a result of load changes.

The deenergization of solenoid 32 results in the opening of the bypass valve as a result ot a reduction in pressure in pressure chamber 64 which is connected to the reservoir conduit 28. This connection is effected through the fitting ltltl, the internal cavity 98 of the solenoid operated valve, passageway 172 in the valve piston 96, needle valve l'd, tube 176, and tting 154. At the same time the intiow of tluid to the pressure chamber through needle valve is shut ofi by valve piston 96. The rate or opening of the bypass valve and thus the rate of stopping of the elevator movement in its up direction is determined by the adjustment of needle valve E74. Ultimately, the bypass valve 4i) is fully opened, the hollow piston 62 being moved to its limiting position to the iight by spring 92 while spring S5 forces the inner piston titl against the shoulder 5"@ of the outer piston.

When the bypass 4i) opens the flow to the elevator jack through conduit lo ceases with the result that valve 5G is seated to prevent any retrograde flow.

The deenergization of solenoid 34 results in the closure of the valve operated by it with the result that a pressure is built up in chamber' 12S to equal the pressure in conduit 26 whereupon the spring 134) moves the piston to the right until the washer 132 abuts against shoulder M4.

To lower the elevator at high speed, the solenoid 36 is energized to effect movement of the valve Sil to a first open position wherein liquid is permitted to flow past it from the elevator jaclt through conduit i6 to the reservoir passage Z8. The valve is opened, by supplying lluid under pressure to the pressure chamber 28, to an extent determined by another slide valve 185i, also mounted in a bore in the closure cap 12e, which bore is closed by a plug 3&2. Fluid under pressure is supplied to the presn sure chamber from the conduit l5 through the solenoid operated valve 36, a needle valve i3d, tube i135, and a port lSl opening into the slide valve bore. The inner face of the piston, it should be noted, is open to reservoir pressure while fluid in conduit i6 is at higher pressure depending upon the Weight of the elevator' and the uid in the elevator ,iaclc As a result uid flows to the pressure chamber TlZli at a rate dependent upon the adjustment of needle valve 134 and the piston 12% is gradually moved to the right. The enlarged end llo encounters the inside portion M4 of the valve Si? and forces it to the right or partially opens it. The piston is moved to the right until the slide valve tdi? (which has an adjusting screw 19d extending through it and engaging the outer face of the piston and which is maintained in engagement with the outer face of the piston by a spring U2) closes the port 23S to such an extent that the flow of fluid into the pressure chamber from conduit lo is equal to the i'iow out of the chamber through the needle valve Mil. It should perhaps be noted that the slide valve has a reduced inner portion 194 permitting the ilow of fluid from port to the pressure chamber and that the slide valve is prevented from rotating by a tangent pin E96.

The elevator will thus be lowered at a rate depending upon the extent ol the opening of valve Sti and the latter is determined by the adjustment of the slide valve 18d. The liquid owing past the valve Si) also lows past the now open bypass valve to the reservoir conduit 28 and thus to the reservoir.

The distance traveled by the elevator in stopping does not vary so much with load when traveling downward as upward because, While a heavier load causes higher pressure and consequently more rapid ilow of liquid through valve 50, it also tends to produce more rapid closure of valve Sil when the solenoid operated valve 36 is closed, because the valve is caused to close chieily by the pressure on the right hand face of the valve acting on piston iowever, beneiit is derived from slowing down the elevator to a reduced descending speed prior to making landing stops and the present device has means for accomplishing this.

To effect slow speed lowering, it is necessary only to energize solenoid operated valve 3S and to deenergize solenoid operated valve 36. This results in partially closing of the valve 50. The mechanism for determining this position is similar to that previously described. It includes another slide valve 200 having a piston face engaging adjustment screw 262, a spring 294 biasing the valve to the right and mounted in a bore in the closure cap l26 closed by a plug 206. It is also prevented from rotating by a tangent pin 208. Liquid is supplied to the pressure chamber under the Control of the slide valve through the solenoid operated valve 38, an adjustable needle valve Zitti, a tube 212 and port 214 which is adapted to be partially closed by the slide valve when the piston moves the valve 5G to an open postion which permits rluid to flow from the elevator jack to the reservoir at a lesser rate. lt will be noted that the only dil-7erence between the arrangements for effecting high and slow speed lowering is that piston 129 moves a greater distance to the right when the slide valve ld is eiiective than when slide valve 294i is effective.

The slide valves 156, 130 and 20u are provided with small passages 216 providing communication between opposite ends thereof so that the pressures will be equalized on opposite sides of them and they will more readily follow the movements of the piston 120.

When the changeover is made from high to slow speed lowering, no fluid flows to the reservoir or to the pressure chamber E30 through the port 188 and initially none lows through the port 214. The piston 120 thus is returned to the left by valve Sil and spring 133, the fluid from the pressure chamber 128 being returned to the reservoir through the needle valve M0. This movement occurs until the port 214 is opened to an extent such that the inllow of iluid equals the outflow.

To stop the downward movement of the elevator, the solenoid 3g is deenergized with the result that lluid is no longer supplied to the pressure chamber 12S. Thus piston 129 will be returned to its normal position by the liquid pressure on valve 50 and by spring 138 and the valve Sti will ultimately be closed and bring the elevator to rest.

According to another feature of the present invention, the device is constructed and arranged so that the bypass valve 40 will open in the event an overload is placed on the elevator or an obstruction encountered. Assume that the elevator is being raised at reduced speed and the valve Sil partly open and the bypass valve 4t) partially closed, as illustrated. In the case of an overload or the encountering of an obstruction, the pressure in conduit 26 will rise above a desired limiting value determined by spring 76 and the latter will be compressed and the disc '72 moved away from seat 73 to reduce the pressure in the pressure chamber 64, whereupon the bypass valve it) will be opened to bypass the liquid. When the overload is encountered, the pressure in conduit 26 increases and this increase also occurs in pressure chamber 64 in a manner described hereinafter. This high pressure acting on that part of the inner piston 60 not covered by disc '72 is applied to the spring 76 and, inasmuch as the latter is adjusted to carry only normal maximum working pressure, it will yield and permit piston 60 to move to the left. Its seat 7S is therefore moved away from the disc 72 with the result that the pressure chamber64 is connected to the reservoir conduit 2S through the passageways 80. There is an immediate and considerable loss of pressure in chamber 64 and both the valve Y40 and piston 6i? will at once move to the right, whereby the bypass is opened to an extent such as to reduce the pressure in conduit 26 to the desired value. At this time the disc 72 and its seat 7S will be separated by only suilicient space to permit the escape of liquid entering through needle valve 94, putting the bypass assembly in equlibrium. Accordingly, the entire llow of the pump or any portion thereof may be passing. through the bypass valve di) at this time. In case the overload or obstruction is removed, the spring 76 expands to bring the disc 72 into engagement with its seat 78. Pressure again builds up in the pressure chamber and the bypass valve 40 is returned to its initial partially closed position. ln the event the bypass valve were closed entirely at the time of the overload or the encounter of an obstruction, the bypass valve would open in the same vmanner as described above and after the removal of the overload or obstruction, it would also be closed as described.

The speeds of the elevator, except for the fast raising, are adjusted by the adjusting screws 158, 190 and 202 associated with the slide valves 156, 180 and 200, respectively. The slow up speed of the elevator is adjusted by the screw 158. Its position `controls the position of the valve 50 when lluid is supplied to the elevator jack to raise the elevator at slow speed, as described above. The position of screw 190 controls the position of valve 56 for high speed lowering of the elevator. It determines the position of piston 120 for high speed ylowering and thus the position of valve 50 which engages the enlarged end 116 of the valve stem. The adjusting screw 202 similarly determines the position of the piston and valve for slow speed lowering.

The various needle valves are provided to adjust the rates at which the principal movements of the valves occur. Needle valve 140 adjusts the rate at which valve 50 closes; with its adjustment established, valves 184 and 210 adjust the rate at which valve 50 opens to full speed down and slow speed down positions,respectively. Valve 94 adjusts the rate of closure of bypass valve 40 and thereby the rate at which the elevator starts upward. Valve 174 adjusts the rate of opening of the bypass valve and thereby the rate of stopping in upward motion. Valve 150 sets the rate at which valve 50 is moved to the throttling position for slow upward movement.

While it is believed that the operation of the apparatus as a whole will be evident from the foregoing detailed description, it will be reviewed briefly.

ln the following description of the operation, it will be assumed that the elevator is at rest at a lower level and is to be raised irst at high speed and then at slow speed. The pump driving motor 30 is deenergized as are all the various solenoid operated valves. The bypass valve is open, it being biased to its open position by the spring 92 and its pressure chamber 64 being connected to the low pressure region of conduit 28 through the passageway 172 in valve piston 96 and the needle valve 174. The combined check and lowering valve 50 is closed by the combined weight of the elevator and iluid in the elevator` jack 14. The piston 120 is'to Vthe right of where it is shown to an extent such'that the washer 132 engages the shoulder 124.

To raise the elevator at high speed, the'pump driving motor 3G is energized as is the Valve operated solenoid 32, whereupon its piston 96 is raised to connect the pressure chamber 64 to the pump outlet conduit 26. As a result, pressure is gradually increased in the pressure chamber at a rate dependentupon the setting of needle valve 94 and the bypass valve 40 is gradually` closed as heretofore described in detail. When the. pressure in conduit 26 exceeds that in the conduit 16, the valve 5i) is moved to its open position with the result'that fluid is supplied through conduitv- 16 to the elevatorl jack to raise'the elevator at high speed.

lTo raise the elevator at slowy speed, as at the approach to an upper landing, the solenoid operated valve 34 is also energized. This results, first, in the partial closure of valve 50 and, second, in the maintenance of a constant rate of Vllow past the valve. The partial closure of valve 5t! is accomplished by connecting the pressure chamber 12S to the low pressure of reservoir conduit 28 through the needle valve 150. The piston thereupon moves to the left to the position indicated and moves the slide-valve 156 until therate of llow of fluid from the pressure chamber through needle valve isl equal to the inflow through the needle valve 140. The rate ofllow past the valve 59 is maintained constant by partial opening of the bypass valve 4d, which partial opening is controlled by the spring loaded check valve 54 in a manner also described in detail hereinabove.

To stop the elevator a't the upper landing, the solenoids 32 'and 34 and the motor 3i) are deenergized. The elevator is stopped as a result 'of the open-in'gof the bypass valve 49, the opening resulting from the connection of the pressure chamber '64 to lthe low pressure region of the elevator is being raised either at high speed or slow speed, the disc 72 yis moved 'away from its cooperating seat 7'8 thereby immediately relieving the pressure in chamber 64 and permitting the bypass valve to open thereby bypassing either part or all of the output of the pump, also as has been' described in detail earlier.

To lower the elevator at high speed, the solenoid operated valve 36is energized thereby building up pressure in the pressure chamber 128 associated with piston 12d. The latter is moved to the right to open the valve 5G to an extent determined by the adjustment of sli-de valve'lStv.

To lower the elevator at slow speed, the solenoid operated valve 36 is deenergized and the solenoid operated valve 33 is energized. The piston v126i then returns to the left to a position determined by the sli-de valve 200, therebyto position lthe valve 5t) in a reduced return `flow position.

To stop the lowering movement of the elevator, the solenoid 3S is deenergized whereupon the valve 59 is closed by the pressure in conduit 16.

While the present invention has been described in connection with a diagrammatic embodiment thereof, it should be understood that various changes may be made therein. For instance, it is contemplated that a commercial structure may have lall parts located Within a housing vand will require no external tubing. Other changes may also be made in. the particular construction of the device by those skilled in the art and the details of the specically described embodiments are not intended to be limitative of the invention, except in so far as set forth in the Iaccompanying claims.

Having thus described my invention, what l claim 4as new yand desire to secure by Letters Patent of the United States is:

l. ln apparatus of the class described, an orifice and means for regulating the ilow of fluid through said orillce, sai-d means including a bypass, a movable tluid flow regulating valve for said bypass, a cylinder, a piston movable in said cylinder and operatively connected to said valve to close said valve as pressure in said `cylinder increases, a lluid conduit connecting said cylinder to the upstream side of said oriiice, a'fluid conduit connecting said cylinder with the downstream side of said or'ice, and a valve controlling ilow through said last mentioned conduit arranged to open 'when the pressure lat the upstream side of said orifice exceeds the pressureat' the downstream side by la predetermined amount.

2. Apparatus of the character described, comprising an orifice, a pressure relief valve upstream of said orifice for regulating the flow of fluid through said orifice, means including a chamber and a piston mounted in said chamber for moving said valve toward `closed position as the pressure in said chamber rises, means for supplying pressure to said chamber from the upstream side of said orifice, and means responsive to the pressure diterential across said orifice for relieving the pressure in said cylinder when said dierential exceeds a predetermined value.

3. Apparatus of the character described, including an orifice, a movable pressure relief valve loc-ated upstream of said orifice for controlling the ow of uid through said orifice, and means responsive to the pressure drop across said orifice for variably positioning said valve to maintain a substantially constant pressure differential across said orifice.

4. In apparatus of the character described, a movable valve, a piste-n operatively connected to said valve, a cylinder in which the piston is movably mounted vand defining with said piston a pressure chamber, and means including valve means adjustably and operatively connected to and movable with said piston Iand responsive to the pressure ditierential across said valve for regulating the pressure in said chamber and positioning said valve.

5. In apparatus of the character described, a movable valve, la piston operatively connected to said valve, a cylinder in which the pist-on is movably mounted and defining with said piston a pressure chamber, and means including a plurality of individually adjustable valve means operatively connected to and movable lwith said piston for regulating the pressure in said chamber and placing said valve in a plurality of positions.

6. In apparatus of the character described, a movable valve, a piston operatively connected to said valve, 'a cylinder in which the piston is movably mounted and defining with said piston a pressure chamber, and means including movable valve means bia-sed toward and movable with said piston and responsive to the pressure `dierential across said valve for regulating the pressure in said chamber and positioning said valve.

7. ln apparatus of the `character described, a movable valve, a piston operatively connected to said valve, a cylinder in which the piston is movably mounted and defining with said piston `a pressure chamber, valve means operatively connected to and movable with said piston controlling the ow of fluid out of said chamber, and means for selectively connecting said valve means to a low pressure region.

8. In apparatus of the character described, 'a pressure chamber including a movable piston, a movable valve for controlling the flow of uid through said valve in opposite directions, 'a lost motion connection 'between the valve and piston permitting limited relative movement between them, and means for selectively moving said piston to two different positions for each direction of ow.

9. in apparatus for controlling the ow of fluid in opposite directions, a movable valve controlling the ow of the liu-id, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between said piston and valve, means for varying the position of said piston to vary the posit-ion of said valve to control the tlow of iiuid in one direction, and other means for varying the position of said piston to control the ilow of Huid in the opposite direction.

10. in apparatus for controlling the flow of tluid in opposite directions, a movable valve controlling the iow of the tiuid, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between said piston and valve, uid connections maintaining a suitable pressure in said chamber for determining one position of said valve for fluid flow in one direction, means including iluid connections and a valve operatively connected to said piston for reducing the pressure in said chamber to move the piston to another position for determining another position of said valve for fluid flow in said one direction, and other mean-s for varying the position of said p-iston to control the ow of fluid in the opposite direction.

11. In apparatus for controlling the flow of uid in opposite directions, a movable valve controlling the flow of the fluid, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between said piston and valve, means for varying the position of said piston to vary the position of said Valve to control the ilow of fluid in one direction, and means including uid connections and a pair of valves operatively connected to said piston for maintaining pressure in said chamber and said piston at different positions to control the flow of fluid in the opposite direction past the valve.

l2. In apparatus for controlling the ow of fluid in opposite directions to and from a uid operated device, a valve port, a movable valve controlling the ow of the fluid through said port located at the downstream side of said port, a pressure chamber including a movable piston one side of which is open to fluid pressure at the upstream side of said port, a lost motion connection between said valve and piston permitting limited relative movement between them, spring means biasing the piston in a direction to move said valve in a direction to open said port, an abutment engaging the valve and determining its movement in said direction, a uid connection from said chamber to the upstream side of said valve whereby equal pressures are maintained at opposite sides of said piston and said valve is kept against said abutment for high rate of fluid flow to said device, means including a iluid connection from said chamber to a low pressure region, means for opening said connection and a valve operatively connected to said piston and movable with it for eliecting movement of said piston to another position and movement of said valve to a partly closed position for a lower rate of fluid ow to said device, and means including a pair of fluid connections to said chamber, means for selectively opening the last said connections, and a valve in each connection operatively connected to and movable with said piston for effecting movement of said piston to different positions whereat said valve is maintained open at different positions against the return ow of lluid to effect the return flow of uid at diFterent rates.

13. In apparatus for controlling the flow of iluid in opposite directions, a port, a movable valve controlling the flow of the fluid through said port, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between them, and means for moving said piston to a position whereat the valve is at one limit of its movement when the iiow is in one direction through said port and the ow of Huid past said port in the opposite direction moves said valve to close said port.

14. In apparatus for controlling the ilow of fluid in one direction, a port, a movable valve controlling the flow of the uid through said port, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between them, an abutment, and means responsive to the pressure differential across said valve for moving said piston to a position whereat the valve is movable against said abutment by the tlow of uid in said one direction.

15. In apparatus for controlling the iiow of fluid in one direction, a port, a movable valve controlling the ow or the uid through said port, a pressure chamber including a movable piston, a lost motion connection between said valve and piston permitting limited relative movement between them, an abutment, means for selectively moving said piston to first position whereat the valve is movable against said abutment by the ow ot fluid in said one direction and to a second position where- 13 in said valve is positioned to restrict the ow of fiuid n said one direction.

16. In apparatus as claimed in claim 15 wherein said piston normally occupies a position wherein the flow of uid in a direction opposite to said one direction moves said valve to close said port.

17. An over-pressure relief device including a bypass valve, a valve stern secured to said valve, a valve disc secured to the outer end of said valve stem, a piston ported to a low pressure region having a valve seat associated with the piston port and adapted to abut against said valve disc, means forming a pressure chamber closed by said piston and disc, and spring means between said valve and piston for urging the latter against said disc.

18. An over-pressure relief device including a bypass valve having a predetermined effective area, a valve stem secured to said valve, a valve disc secured to the outer end of said valve stem, a piston ported to a low pressure region having a Valve seat associated with the piston port and adapted to abut against said valve disc, means forming a pressure chamber closed by said piston and disc, and spring means between said bypass valve and piston for urging the later against said disc, a second piston encircling said first piston, said pistons being relatively.

movable and said first mentioned piston having an effective area equal to that of said bypass valve.

19. An overpressure relief device including a poppet type relief valve, a second smaller valve member connected to move with said relief valve, a piston ported to a low pressure region having a valve seat communicating with said piston port, said second valve member being adapted to close against said seat when said piston is moved away from said relief valve, spring means adapted to urge said piston away from said relief valve, means forming a pressure chamber closed by said piston and second valve, means for introducing fiuid under pressure to said chamber to move said piston, said spring means and said relief valve poppet as a unit to close said relief valve, and said relief valve being adapted to move said second valve away from said seat to vent said chamber upon an application of sufficient pressure to said relief valve to compress said spring.

20. An overpressure relief device including a poppet type relief valve, a second smaller valve member connected to move with said relief valve, a first piston ported to a low pressure region having a valve seat communicating with said piston port, said second valve member being adapted to close against said seat when said first piston is moved away from said relief valve, spring means adapted to urge said first piston away from said relief valve, means forming a pressure chamber closed by said first piston and second valve, restricted means for introducing fiuid under pressure to said chamber to move said first piston said spring means and said relief valve as a unit to close said relief valve, said relief valve poppet being adapted to move said second valve away from said seat to vent said chamber upon an application of sufficient pressure to said relief valve to compress said spring, a second piston encircling said first piston, said pistons being relatively movable, spring means acting between said pistons tending to urge said second piston away from said poppet, and said first piston having an area substantially equal to said poppet.

21. An overpressure relief device for controlling ow through an orifice including a poppet type relief valve, a second smaller valve member connected to move with said relief valve, a first piston ported to a low pressure region having a valve seat communicating with said piston port, said second valve member being adapted to close against said seat when said first piston is moved away from said relief valve, spring means adapted to urge said first piston away from said relief valve, means forming a pressure chamber closed by said first piston and second valve, restricted means for introducing uid under pressure to said chamber to move said first piston, said spring means and said relief valve as a unit to close said relief valve, means for venting said chamber to the region downstream of said orifice when the pressure in said chamber exceeds said downstream pressure by a predetermined amount, said relief valve poppet being adapted to move said second valve away from said seat to vent said chamber upon an application of sufficient pressure to said relief valve to compress said spring, a second piston encircling said first piston, said pistons being relatively movable, spring means acting between said pistons tending to urge said second piston away from said poppet, and said first piston having an area substantially equal to said poppet.

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